Semiconductor production technology that achieves further miniaturization has been developed, and a line width of 20 nm or 10 nm has been used for a leading-edge process. The degree of difficulty in processing has increased along with an increase in the degree of miniaturization, and various techniques are currently under development using various approaches in terms of the materials, devices, processing methods, and the like.
In view of the above situation, the applicant of the present application developed a plasma etching gas that can deal with a leading-edge plasma etching process, and found that a saturated non-methane fluorohydrocarbon having a small number of fluorine atoms exhibits performance better than that of monofluoromethane that is widely used at present for etching a silicon nitride film (see Patent Literature 1).
However, semiconductor production technology that achieves further miniaturization has been developed in recent years, and higher performance has been desired for a plasma etching gas used for a plasma etching process.
It is known that isobutyl fluoride and t-butyl fluoride can be produced using several different methods.    (a) The following method is known as a method for producing isobutyl fluoride.
Patent Literature 2 discloses a method that reacts isobutyl alcohol with chlorotrimethylsilane in the presence of pyridine to obtain 1-trimethylsiloxy-2-methylpropane and brings 1-trimethylsiloxy-2-methylpropane into contact with diethylaminosulfur trifluoride (fluorinating agent) to obtain a mixture including isobutyl fluoride and t-butyl fluoride.    (b) With regard to a method for producing t-butyl fluoride, Patent Literature 3 discloses that t-butyl fluoride was produced by bringing an n-pentane solution of t-butyllithium into contact with sulfur hexafluoride.
Non-Patent Literature 1 discloses that t-butyl fluoride was obtained in a yield of 78% by bringing t-butanol into contact with a diethylamine adduct of hexafluoropropene (fluorinating agent).
Non-Patent Literature 2 discloses that t-butyl fluoride was obtained in a yield of 60% by treating t-butanol with 60% hydrofluoric acid.
Non-Patent Literature 3 discloses that t-butyl fluoride was obtained in a yield of 60% by adding hydrogen fluoride to 2-methylpropene using a hydrogen fluoride-pyridine complex as a fluorinating agent.